DESCRIPTION (Applicant's Abstract): There is no proven safe and effective treatment for tardive dyskinesia which remains a major concern in psychiatry. At present, conventional antipsychotic drugs have all been associated with risk of tardive dyskinesia development. The major question now is whether or not the new 'novel' or 'atypical' antipsychotic will produce significantly less tardive dyskinesia than conventional drugs. This question is of enormous clinical economic and heuristic importance and will not be answered in a timely fashion unless appropriate, focused methodology is brought to bear. The present proposal will prospectively determine the incidence of tardive dyskinesia in a sample of high risk patients (individuals over the age of 55) being treated with antipsychotic drugs for the first time under routine clinical care. Patients receiving either of two new-generation antipsychotic drugs, risperidone or olanzapine, will be included and followed longitudinally. Two hundred sixty patients starting on each drug will be included. The incidence of new cases of TD will be contrasted with data from a previous study of 261 patients treated with conventional antipsychotics and followed prospectively from the initiation of treatment. This strategy will provide a rapid and cost-effective answer to a critical question.